1. Field
The present disclosure relates to the field of olefin polymerization. It more particularly relates to processes for feeding ethylene monomer into one or more polymerization reactors. Still more particularly, the present disclosure relates to processes for feeding ethylene monomer dissolved in one or more C3-C20 monomers and/or C4-C20 saturated aliphatic or aromatic hydrocarbons, and combinations thereof to improve compositional control of the reactor input feed streams, and to reduce the investment and operation costs associated with ethylene feeding in the production of ethylene-containing polymers and polymer blends.
2. Description of the Related Art
In prior art processes for making copolymers of ethylene and C3-C20 higher olefins in polymerization systems operating in a liquid phase or a supercritical phase, ethylene is typically delivered to the reactor in gaseous form by compressors. Such compressors are expensive to install and operate, particularly in high-pressure polymerization processes operating above 100 atm (1450 psi), or above 350 atm (5075 psi). The C3-C20 higher olefins, such as, for example, propylene, butenes, butene-1, butene-2, isobutylene, pentene-1, hexene-1, heptene-1, octene-1, decene-1, styrene, o-methylstyrene, p-methylstyrene, 1,3-butadiene, 1,5-hexadiene, 1,7-octadiene, 1,9-decadiene, divinylbenzene, dicyclopentadiene, norbornene, norbornadiene, vinylnorbornene, ethylidenenorbornene, etc., are typically delivered to the reactor in liquid form by a pump. The precise control of feed composition, i.e., the ratio of ethylene to the C3-C20 olefin components, is typically difficult due to the lack of flow control devices capable of operating at high pressures, particularly above 100 atm (1450 psi), or above 350 atm (5075 psi). The separate feeding of ethylene by one or more compressors also lacks flexibility in terms of feed composition for allowing both low (0.1-5.0 wt %) and high (up to 70 wt %) ethylene contents in the feed on an ethylene/(ethylene+higher olefin) basis. Delivering ethylene separately to the reactor by compressors also increases capital and operating cost.
Hence, a need exists for an improved process for feeding ethylene monomer to one or more reactors operating in a liquid phase or a supercritical phase to allow for improved compositional control and reduced capital and operating costs in the production of ethylene-containing copolymers.